Legion I. SPUMELLARIA, (continued 13)

The genus Ommatodiscus, together with the following Stomatodiscus, form the peculiar small subfamily of Ommatodiscida, founded by Stöhr in 1880 (loc. cit.). These remarkable Porodiscida, very nearly allied to Porodiscus, are distinguished by one or two large openings on the margin of the disk, and these "marginal oscula" are constantly armed with a coronet of spines (comparable to the osculum coronatum of Sycon in the Calcispongiæ). Probably in the living Ommatodiscida the osculum is the door from which a "sarcode-flagellum" issues (comp. above, p. 407). Perhaps this osculum is comparable to the peculiar coronet of spines which is developed on one pole of the shell axis in some Ellipsida (Lithomespilus, Lithapium). The internal structure of the disk is commonly more or less obscure, as the lenticular disk is much thickened, sometimes nearly ellipsoidal. It is possible that the Ommatodiscida are more nearly related to the Lithelida than to the Porodiscida; but there is no indication of an internal trizonal medullary shell. Also the apparent resemblance to the Cyrtida is of no morphological value; both groups are of quite independent phylogenetic origin.

Subgenus 1. Ommatodiscinus, Haeckel.

Definition.—Disk circular.

1. Ommatodiscus decipiens, Stöhr.

Ommatodiscus decipiens, Stöhr, 1880, Palæontogr., vol. xxvi. p. 115, Taf. vi. figs. 8, 8a.

Disk circular, with two chambered rings around the spherical central chamber, of equal breadth. Chambers twice as high as broad. Pores very small, one-third as broad as the bars between them, two on the breadth of each ring. Osculum of the same breadth as the central chamber, surrounded by numerous very short teeth.

Dimensions.—Diameter of the disk 0.12; breadth of the central chamber and of each ring 0.03; pores 0.0015.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

2. Ommatodiscus stöhrii, n. sp.

Disk circular with three chambered rings around the spherical central chamber, of equal breadth. Chambers broader than high. Pores of the same breadth as the bars between them, four on the breadth of each ring. Osculum of the same breadth as the central chamber, surrounded by a corona of ten to twenty thin, bristle-shaped teeth, as long as its diameter.

Dimensions.—Diameter of the disk 0.2; breadth of the central chamber and of each ring 0.03; pores 0.004.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

3. Ommatodiscus circularis, n. sp.

Disk circular, with four circular chambered rings around the spherical central chamber, of increasing breadth; the fourth ring twice as broad as the second. Chambers about as broad as high. Pores large, twice as broad as the bars, one to two on the breadth of each ring. Osculum twice as broad as the central chamber, surrounded by a coronal of strong conical teeth, twice as long as its diameter.

Dimensions.—Diameter of the disk 0.18; breadth of the central chamber and inner rings 0.015, of the outer rings 0.03; pores 0.01.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

Subgenus 2. Ommatodisculus, Haeckel.

Definition.—Disk elliptical.

4. Ommatodiscus haeckelii, Stöhr.

Ommatodiscus haeckelii, Stöhr, 1880, Palæontogr., vol. xxvi. p. 115, Taf. vi. figs. 7, 7a.

Disk elliptical (6 : 7), with four chambered rings around the elliptical central chamber, of equal breadth. Chambers about as high as broad. Pores small, half as broad as the bars, two on the breadth of each ring. Osculum three times as broad as the central chamber, surrounded by a crown of strong conical teeth.

Dimensions.—Length of the disk 0.18, breadth 0.16; breadth of each ring and of the central chamber 0.02; pores 0.003.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte (Stöhr), Caltanisetta (Haeckel).

5. Ommatodiscus lævigatus, Stöhr.

Ommatodiscus lævigatus, Stöhr, 1880, Palæontogr., vol. xxvi. p. 116, Taf. vi. figs. 9, 9a.

Disk elliptical (3 : 4), with three chambered rings around the circular central chamber, the third ring half as broad as the second. Chambers twice as high as broad. Pores very small, one-third as broad as the bars. Osculum twice as broad as the central chamber, armed with a crown of short conical teeth.

Dimensions.—Length of the disk 0.15, breadth 0.11; breadth of inner rings 0.02, of the outer 0.01; pores 0.0017.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

6. Ommatodiscus fragilis, Stöhr.

Ommatodiscus fragilis, Stöhr, 1880, Palæontogr., vol. xxvi. p. 116, Taf. vi. figs. 10, 10a.

Disk elliptical (4 : 5), with five chambered rings around the elliptical central chamber, the fifth ring twice as broad as each of the others. Chambers about as high as broad. Pores very small, one-fifth as broad as the bars. Osculum three times as broad as the central chamber, surrounded by a coronet of short teeth.

Dimensions.—Length of the disk 0.17, breadth 0.13; breadth of the inner rings 0.01, of the outer 0.02; pores 0.001.

Habitat.—Fossil in Tertiary rocks of Sicily and Barbados; living in depths of the Tropical Atlantic and Pacific, Station 353, depth 2965 fathoms, Station 265, depth 2900 fathoms, &c.

Genus 217. Stomatodiscus,^[256] n. gen.

Definition.—Porodiscida without chambered arms and radial spines on the margin of the circular or elliptical disk, but with two large, opposite, marginal oscula, or openings surrounded by a coronet of spines.

The genus Stomatodiscus has the same characteristic structure as the foregoing Ommatodiscus, and differs from it only in the duplication of the large marginal openings. Whilst in the latter there is only one such marginal osculum, here we find on the margin of the disk two oscula, opposite on the poles of one equatorial axis.

1. Stomatodiscus amphistomus, n. sp.

Disk circular, with three concentric rings of equal breadth around the central chamber. Pores irregular, roundish, about two on the breadth of each ring. Surface of the lenticular shell spiny. On two opposite points of the margin a large osculum, three to four times as broad as the central chamber, armed with a coronet of strong pyramidal spines of different length, the longest equal to the radius of the disk.

Dimensions.—Diameter of the disk (with three rings) 0.12; breadth of each ring 0.016; pores 0.004.

Habitat.—South Pacific, Station 302, depth 1450 fathoms.

2. Stomatodiscus osculatus, n. sp. (Pl. 48, fig. 8).

Disk elliptical, nearly twice as long as broad, with three concentric rings around the elliptical central chamber, one piercing radial beam in the main axis, the other beams interrupted. Surface of the shell with small scattered thorns. Pores very irregular, roundish, partly aggregated in groups of four to eight smaller porules. On both poles of the main axis a large elliptical marginal osculum, about as large as the central chamber, armed with a coronet of short conical spines.

Dimensions.—Length of the disk (with three rings) 0.18, breadth 0.1; pores 0.001 to 0.006.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Subfamily 4. Stylodictyida, Haeckel, 1881, Prodromus, p. 459.

Definition.—Porodiscida with solid radial spines on the margin of the concentrically annulated disk, situated in the equatorial plane of the disk (without chambered arms and marginal oscula).

Genus 218. Xiphodictya,^[257] Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with two opposite, solid, radial spines on the margin of the circular or elliptical disk.

The genus Xiphodictya opens the series of the Stylodictyida or of those Porodiscida in which the margin of the chambered disk is armed with solid radial spines, all situated in the equatorial plane of the disk. Xiphodictya exhibits the minimum number of spines, two being opposite on the poles of one equatorial axis of the disk. It repeats, therefore, in this family the same amphistylic formation as Sethostylus in the Phacodiscida and Stylocyclia in the Coccodiscida.

Subgenus 1. Xiphodictyon, Haeckel.

Definition.—All rings of the disk concentric, circular.

1. Xiphodictya amphibelonia, n. sp. (Pl. 42, fig. 10).

All rings of the disk concentric, circular, of equal breadth. Pores irregular, roundish, one and a half to two on the breadth of each ring. Margin of the disk thorny, of the same thickness as the central part of the medal-shaped or cylindrical disk. Two opposite radial spines very long and thin, cylindrical, twice to three times as long as the diameter of the disk, only half as thick as the breadth of one ring.

Dimensions.—Diameter of the disk (with five rings) 0.17; breadth of each ring 0.014; pores 0.003 to 0.012.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

2. Xiphodictya amphirrhopalia, n. sp. (Pl. 42, fig. 11).

All rings of the disk concentric, circular, with increasing breadth from the centre; the fifth ring twice as broad as the second. Central chamber very large. Margin of the lenticular disk thorny, much thinner than the central part. Pores irregular, roundish, two to three on the breadth of each ring. Two opposite radial spines club-shaped, about as long as the diameter of the disk, in the outer spindle-shaped part three to four times as broad as at the base.

Dimensions.—Diameter of the disk (with six rings) 0.17; breadth of the second ring 0.008, of the fifth ring 0.016.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms; also fossil in the Tertiary rocks of Sicily (Caltanisetta).

Subgenus 2. Xiphospira, Haeckel.

Definition.—All rings of the disk or a part of them not concentric, spirally convoluted; sometimes irregular or interrupted.

3. Xiphodictya staurospira, n. sp. (Pl. 42, fig. 12).

All rings of the disk not concentric, half spiral. Four radial beams, crossed perpendicularly and zigzag-shaped, divide each ring into four quadrants; the quarter-ring of each quadrant halves the two adjacent rings. All rings of equal breadth. Pores irregular, roundish, two on the breadth of each ring. Two opposite radial spines pyramidal, somewhat shorter than the diameter of the disk.

Dimensions.—Diameter of the disk (with six rings) 0.16; breadth of each ring: 0.014; pores 0.003 to 0.007.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

4. Xiphodictya heliospira, n. sp.

All rings of the disk not concentric, convoluted in a simple, regular, spiral line; all nearly of equal breadth. Pores subregular, circular, two on the breadth of each ring. Two opposite radial spines conical, about as long as the radius of the disk. Margin of the disk thorny. (Differs from Stylodictya heliospira, Pl. 41, fig. 8, mainly by the two strong, opposite, radial spines.)

Dimensions.—Diameter of the disk (with six rings) 0.14; breadth of each ring 0.01 to 0.012; pores 0.002 to 0.006.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

Genus 219. Tripodictya,^[258] Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with three solid, equidistant, radial spines on the margin of the circular or triangular disk.

The genus Tripodictya exhibits three radial spines on the margin of the disk, divergent at equal angles; rarely in some specimens the angles differ more or less. Perhaps this genus bears a near relation to the Dictyastrida (or to the Euchitonida with three chambered arms—Dictyastrum, Euchitonia, &c.).

1. Tripodictya trigonaria, n. sp. (Pl. 42, fig. 8).

All rings of the disk concentric, triangular, with three equal convex sides, all of the same breadth; first and second rings with three simple chambers, third and fourth rings with six chambers, fifth ring with twelve chambers. Central chamber also equilateral triangular, from its three corners arise three piercing perradial beams; from the second ring arise three interradial beams, alternate with the latter; from the fourth ring between these and the former arise six adradial beams. Pores subregular, two on the breadth of each ring. Three marginal spines pyramidal, as long as the radius of the disk and as broad as one ring.

Dimensions.—Diameter of the disk (with five rings) 0.11; breadth of each ring 0.011; pores 0.004.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

2. Tripodictya triacantha, n. sp. (Pl. 42, fig. 7).

All rings of the disk concentric, circular, of the some breadth, connected by very numerous irregular radial beams, the number of which increases towards the periphery. Pores irregular, roundish, two on the breadth of each ring. Three marginal spines spindle-shaped, as long as the radius of the disk, and in the middle part as broad as one ring.

Dimensions.—Diameter of the disk (with eight rings) 0.2; breadth of each ring 0.012; pores 0.004.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

3. Tripodictya tribelonia, n. sp. (Pl. 42, fig. 9).

All rings of the disk, or a part of them, not concentric, spirally convoluted, of equal breadth, connected by numerous irregular, interrupted radial beams, the number of which increases from the centre. (In one marginal view of the disk, Pl. 42, fig. 9, the disk seemed to be composed of seven parallel chambered plates in the central part, and five similar plates in the peripheral part.) Pores irregular, roundish, three on the breadth of each ring. Three marginal spines long and thin, cylindrical (as in Staurodictya cruciata, Pl. 42, fig, 4), longer than the diameter of the disk, and half as thick as one ring.

Dimensions.—Diameter of the disk (with nine rings) 0.18; breadth of each ring 0.01; pores 0.002 to 0.004.

Habitat.—Pacific, central area, Station 263, depth 2650 fathoms.

Genus 220. Staurodictya,^[259] Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with four solid radial spines (commonly crossed at right angles) on the margin of the circular or quadrangular disk.

The genus Staurodictya is characterised by four marginal spines, lying opposite in pairs in two crossed equatorial diameters of the disk, perpendicular one to another. Sometimes the regular rectangular position of the spines becomes more or less irregular. Commonly the marginal spines are the extreme prolongations of four internal crossed radial beams, which are either rectilinear or zigzag-shaped. In the latter case the concentric disposition of the circular rings becomes more or less spiral. Perhaps Staurodictya has a near relation to the Stauralastrida (or to the Euchitonida with four crossed chambered arms—Stauralastrum, Histiastrum, &c.).

Subgenus 1. Staurodictyon, Haeckel.

Definition.—All rings of the disk concentric (commonly circular, sometimes with four incisions, produced by two crossed constrictions, or nearly square).

1. Staurodictya medusa, n. sp. (Pl. 42, fig. 3).

All rings of the disk concentric, of nearly equal breadth, divided into four quadrants by two perradial constrictions (perpendicular one to another). Pores irregular, roundish, two to three on the breadth of each ring. Four marginal spines strong, pyramidal, nearly as long as the radius of the disk. Margin between them denticulated.

Dimensions.—Diameter of the disk (with four rings) 0.13; breadth of each ring 0.015; pores 0.002 to 0.01.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

2. Staurodictya ciliata, n. sp. (Pl. 42, fig. 2).

All rings of the disk concentric, of nearly equal breadth, circular or roundish, without perradial constrictions. Pores subregular, circular, three to four on the breadth of each ring. Four marginal spines short, pyramidal, about as long as the breadth of one ring. Margin between them ciliated, with thin radial bristles.

Dimensions.—Diameter of the disk (with four rings) 0.13; breadth of each ring 0.015; pores 0.0025.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

3. Staurodictya elegans, n. sp. (Pl. 42, fig. 1).

All rings of the disk concentric, circular, or roundish, of increasing breadth towards the margin; the fifth ring twice as broad as the first. Pores irregular, roundish, two to three on the breadth of each ring. Four marginal spines very large, conical, with a thin pedicle at the base, cancellated by ten to twelve deep furrows, about as long as the radius of the disk and three times as long as broad at the base (above the pedicle). Margin between them ciliated, with numerous short radial spines.

Dimensions.—Diameter of the disk (with six rings) 0.14; breadth of the inner rings 0.006, of the outer 0.012; pores 0.002 to 0.008.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

4. Staurodictya quadrispina, Haeckel.

Stylodictya quadrispina, Haeckel, 1862, Monogr. d. Radiol., p. 496, Taf. xxix. fig. 4.

All rings of the disk concentric, circular, of increasing breadth towards the margin; the fourth ring twice as broad as the second. Pores irregular, roundish, two to three on the breadth of each ring. Four marginal spines short and thin, conical, about as long as the breadth of one ring. Margin between them smooth.

Dimensions.—Diameter of the disk (with six rings) 0.12; breadth of the inner rings 0.006, of the outer rings 0.012; pores 0.001 to 0.006.

Habitat.—Mediterranean, Atlantic (Canary Islands), surface.

Subgenus 2. Staurospira, Haeckel.

Definition.—All rings of the disk or a part of them not concentric, spirally convoluted; spiral line simple or double, sometimes half or irregular, interrupted.

5. Staurodictya cruciata, n. sp. (Pl. 42, figs. 4, 5).

All rings of the disk nearly of the same breadth, not concentric, half-spiral, interrupted by four zigzag-shaped radial beams crossed in two diameters perpendicular one to another. The quarter ring of each quadrant halving both neighbouring quarters. Pores irregular, roundish, two on the breadth of each ring. Pores of the outermost (eighth) ring much smaller than the others. Four marginal spines cylindrical or nearly spindle-shaped, thick, about as long as the radius of the disk. Margin between them smooth.

Dimensions.—Diameter of the disk (with eight rings) 0.2; breadth of each ring 0.011; pores 0.004.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

6. Staurodictya splendens, Haeckel.

Stylodictya splendens, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxiii. fig. 9.

All rings of the disk nearly of the same breadth, not concentric, half-spiral, interrupted by four zigzag-shaped perradial beams, crossed in two diameters. The quarter ring of each quadrant halving both neighbouring quarters. Pores regular, circular, only one single on the breadth of each ring. Four marginal spines conical or spear-shaped, about half as long as the radius of the disk. Margin between them ciliated, with short bristle-shaped radial spines.

Dimensions.—Diameter of the disk (with eight rings) 0.2; breadth of each ring 0.012; pores 0.004.

Habitat.—Fossil in the rocks of Barbados.

7. Staurodictya grandis, n. sp.

All rings of the disk (twelve to sixteen) of the same breadth, not concentric, irregular, partly spiral, interrupted by irregular turnings, and by ramified radial beams, which divide each ring into numerous square chambers. Pores subregular, circular, only one single on the breadth of each ring (and on each chamber). Four marginal spines short and stout, conical, twice as long as broad at the base, four to five times as long as the breadth of one ring. Margin between them dentated.

Dimensions.—Diameter of the disk (with sixteen rings) 0.3; breadth of each ring 0.01; pores 0.005.

Habitat.—Pacific, central area, Stations 265 to 268, depth 2900 fathoms; also fossil in the Tertiary rocks of Barbados.

8. Staurodictya ocellata, Haeckel.

Stylodictya ocellata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxiii. fig. 7.

All rings of the disk irregular, not concentric, half-spiral, interrupted by four zigzag-shaped, crossed, radial beams; the quarter ring of each quadrant halving both neighbouring quarters. Breadth of the rings increasing towards the periphery; the fourth ring twice as broad as the second. Pores irregular, with increasing size from the centre, three on the breadth of each ring. Four marginal spines thick and long, cylindrical; margin between them smooth.

Dimensions.—Diameter of the disk (with four rings) 0.1; breadth of the inner rings 0.01, of the outer 0.02; pores 0.002 to 0.006.

Habitat.—Fossil in the rocks of Barbados.

Stylodictya haeckelii, Zittel, 1876, L. N. 29, p. 85, Taf. ii. fig. 9, is a fossil Cretaceous species, related to Stylodictya multispina.

Genus 221. Stylodictya,^[260] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Porodiscida with numerous (five or more, commonly eight to twelve) solid radial spines, regularly or irregularly disposed on the margin of the circular or polygonal disk; margin simple, without a porous equatorial girdle.

The genus Stylodictya comprises the majority of this subfamily, in which the number of the marginal spines exceeds four. Commonly we find eight to twelve spines, more or less regularly disposed (four perradial and four interradial, or four perradial and eight adradial); but often also the number and disposition become irregular (sometimes very large). In my Monograph (1862 pp. 495, 515) I had separated the concentric disks with closed circular rings (as true Stylodictya, s. str.) from the spiral disks with convoluted rings (Stylospira). But I retain these two groups here only as two subgenera, as intermediate forms between them are very common, and often a part of the disk concentric, a part spiral (compare above, p. 492).

Subgenus 1. Stylodictyon, Haeckel, 1862, Monogr. d. Radiol., p. 495.

Definition.—All rings of the disk concentric, commonly circular (rarely a little elliptical or polygonal).

1. Stylodictya gracilis, Ehrenberg.

Stylodictya gracilis, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 28.

Stylodictya gracilis, Ehrenberg, 1873, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 257; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. xxiii. fig. 3.

Stylodictya gracilis, Haeckel, 1862, Monogr. d. Radiol., p. 499.

All rings of the disk concentric, circular, of equal breadth (the first ring sometimes, but not constantly, four-lobed). Pores regular, circular, small, three on the breadth of each ring. Four perradial beams (crossed in two perpendicular diameters) beginning from the circular central chamber, four interradial beams from the first or second ring (sometimes others between them). Beams prolonged into eight to twelve (or more) marginal spines, bristle-shaped, as long as the radius of the shell.

Dimensions.—Diameter of the disk (with four rings) 0.12; breadth of each ring 0.013; pores 0.0025.

Habitat.—Fossil in Tertiary rocks of Barbados and Nicobar; living in the depths of the Pacific and Atlantic.

2. Stylodictya multispina, Haeckel.

Stylodictya multispina, Haeckel, 1862, Monogr. d. Radiol., p. 496, Taf. xxix. fig. 5.

Stylodictya forbesii, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 160, Taf. xxiii. fig. 6.

All rings of the disk concentric, circular, of equal breadth. Pores regular, circular, two and a half to three on the breadth of each ring. Eight to twelve radial beams beginning from the central chamber, others from the inner rings. Commonly from the third or fourth ring arise twenty-four to thirty (sometimes forty or more) piercing beams, which are prolonged at the margin into bristle-shaped radial spines, as long as the breadth of two to four rings.

Dimensions.—Diameter of the disk (with seven rings) 0.2; breadth of each ring 0.013; pores 0.004.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface and various depths.

3. Stylodictya hastata, Ehrenberg.

Stylodictya hastata, Ehrenberg, 1873, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 257; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. xxiii. fig. 5.

Stylodictya gracilis, Bury, 1862, Polycystins of Barbados, pl. ii. fig. 1.

All rings of the disk concentric, circular, of equal breadth. Pores regular, circular, very small, two on the breadth of each ring. Eight to twelve marginal spines very large, spear-shaped, sulcated, pyramidal, nearly as long as the diameter of the disk, with a thin pedicle at the base, above this as thick as the breadth of one ring.

Dimensions.—Diameter of the disk (with five rings) 0.13; breadth of each ring 0.012; pores 0.003.

Habitat.—Fossil in the rocks of Barbados.

4. Stylodictya stellata, Bailey.

Stylodictya stellata, Bailey, 1856, Amer. Journ., vol. xxii. p. 6, pl. i. fig. 20.

Stylodictya stellata, Haeckel, 1862, Monogr. d. Radiol., p. 499.

All rings of the disk concentric, circular, of equal breadth. Pores regular, circular, very small, two on the breadth of each ring. Marginal spines fourteen (probably variable in number, twelve to sixteen), very thick and short, conical; their length seems to be equal to their basal breadth and to the breadth of one ring. Related to Stylochlamydium?

Dimensions.—Diameter of the disk (with five rings) 0.11; breadth of each ring 0.01; pores 0.003.

Habitat.—North Pacific, depths of the Kamtschatka Sea, Bailey; Station 241, depth 2300 fathoms.

5. Stylodictya arachnia, Haeckel.

Stylodictya arachnia, Haeckel, 1862, Monogr. d. Radiol., p. 497.

Stylocyclia arachnia, J. Müller, 1856, p. 492; Abhandl. d. k. Akad. d. Wiss. Berlin, 1858, p. 41, Taf. i. figs. 8, 9.

All rings of the disk concentric, circular, or polygonal; their breadth increases from the centre towards the periphery, so that the fourth or fifth ring is twice as broad as the second. Pores subregular, circular, two on the breadth of each ring. Radial beams partly piercing. Marginal spines eight to sixteen (commonly twelve), bristle-shaped, very thin, once to three times as long as the diameter of the disk. (On the numerous varieties of this common species compare my Monograph, 1862, p. 498.)

Dimensions.—Diameter of the disk (with ten rings) 0.22; breadth of the inner rings 0.004 to 0.008, of the outer 0.012 to 0.015; pores 0.003 to 0.005.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface.

6. Stylodictya solmaris, n. sp.

All rings of the disk concentric, polygonal, with eight to sixteen rounded corners; their breadth increases from the centre; eighth ring twice as broad as the second. Pores subregular circular, large, only one pore on the breadth of each ring. Twenty to thirty marginal spines, bristle-shaped, undulating, about as long as (or longer than) the diameter of the disk.

Dimensions.—Diameter of the disk (with eight rings) 0.2; breadth of the inner rings 0.005, of the outer 0.012; pores 0.004 to 0.008.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

7. Stylodictya octogonia, n. sp.

All rings of the disk concentric, increasing in breadth from the centre. The outer rings (five to eight) regular, octogonal, twice as broad as the circular inner rings. Pores subregular, circular, two to three on the breadth of each ring. Eight piercing perradial spines (alternating with the eight corners of the octogonal rings) bristle-shaped, longer than the diameter of the disk.

Dimensions.—Diameter of the disk (with eight rings) 0.24; breadth of the inner rings 0.006, of the outer 0.014; pores 0.005 to 0.01.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

Subgenus 2. Stylodictula, Haeckel.

Definition.—Rings of the disk partly concentric, completely annular; partly spiral or interrupted, often irregular.

8. Stylodictya perispira, n. sp.

Inner rings of the disk (two to four) concentric, circular, or roundish, outer rings forming a simple spiral, breadth a little increasing from the centre. Pores subregular, circular, about two on the breadth of each ring. Marginal spines bristle-shaped, ten to fifteen, about as long as the diameter of the disk.

Dimensions.—Diameter of the disk (with eight rings) 0.2; breadth of each ring 0.013; pores 0.004.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

9. Stylodictya centrospira, n. sp. (Pl. 41, fig. 9).

Inner rings of the disk (three or four) convoluted in a simple or double spiral, often interrupted or irregular; outer rings (two to three) concentric, circular, or roundish. Breadth of the rings variable, irregular. Pores irregular, of very different sizes, in the outer concentric part twice to four times as large as in the inner spiral part. Radial beams partly interrupted, partly piercing. Marginal spines fifty to eighty, very variable in size and number, commonly fifteen to twenty strong conical spines, twice to three times as long as the ring-breadth, and numerous (thirty to sixty) smaller spines. Very variable.

Dimensions.—Diameter of the disk (with seven rings) 0.2; breadth of the rings 0.01 to 0.02; pores 0.002 to 0.01.

Habitat.—Pacific, central area, Stations 263 to 274, depth 2350 to 2925 fathoms.

10. Stylodictya setigera, Ehrenberg.

Stylodictya setigera, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxiii. fig. 4.

Inner rings of the disk (two to three) convoluted in a simple or double spiral, outer rings (two to three) concentric, circular, or roundish. Breadth of the rings nearly equal. Pores regular, circular, three on the breadth of each ring. Marginal spines twenty to forty, bristle-shaped, about twice as long as the ring-breadth. (The specimen figured by Ehrenberg was a young one; in older specimens I found the inner spiral disk surrounded by two to three concentric circular rings.)

Dimensions.—Diameter of the disk (with six rings) 0.16; breadth of the rings 0.12; pores 0.003.

Habitat.—Fossil in the rocks of Barbados; also living in the depths of the Central Pacific, Station 266, depth 2750 fathoms.

Subgenus 3. Stylospira, Haeckel, 1862, Monogr. d. Radiol., p. 515.

Definition.—All rings of the disk convoluted in a simple or double spiral (sometimes also in quartered half-spirals).

11. Stylodictya heliospira, n. sp. (Pl. 41, fig. 8).

Stylospira heliospira, Haeckel, 1879, MS.

All rings of the disk convoluted in a simple regular spiral, increasing in breadth from the centre towards the periphery; the sixth ring twice as broad as the second. Pores irregular, roundish, two on the breadth of each ring. Marginal spines numerous, thirty to forty, bristle-shaped, nearly half as long as the radius of the disk.

Dimensions.—Diameter of the disk (with seven rings) 0.16; breadth of the inner rings 0.008, of the outer 0.016; pores 0.002 to 0.006.

Habitat.—Mediterranean, Portofino near Genoa, surface; also fossil in the Tertiary rocks of Sicily; Caltanisetta, Haeckel.

12. Stylodictya hertwigii, Haeckel.

Stylospira arachnia, R. Hertwig, 1879, Organismus d. Radiol., p. 59, Taf. vi. fig. 8.

All rings of the disk convoluted in a simple regular spiral, with increasing breadth from the centre; the fifth ring twice as broad as the second. Pores regular, circular, two on the breadth of each ring. Twelve piercing radial beams and some others interrupted, prolonged into twelve to twenty radial marginal spines, bristle-shaped, about as long as the diameter of the disk.

Dimensions.—Diameter of the disk (with five rings) 0.15; breadth of the second ring 0.01, of the fifth 0.02; pores 0.006.

Habitat.—Mediterranean (Messina), R. Hertwig.

13. Stylodictya dujardinii, Haeckel.

Stylospira dujardinii, Haeckel, 1862, Monogr. d. Radiol., p. 515, Taf. xxix. figs. 9, 10.

All rings of the disk convoluted in a simple regular spiral, of nearly equal breadth. Pores regular, circular, two on the breadth of each ring. Very numerous (twenty to thirty or more) piercing radial beams, prolonged into bristle-shaped marginal spines, about as long as the diameter of the disk.

Dimensions.—Diameter of the disk (with six rings) 0.12; breadth of each ring 0.01; pores 0.004.

Habitat.—Mediterranean (Messina), Haeckel.

14. Stylodictya echinastrum, Ehrenberg.

Stylodictya echinastrum, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxiii. fig. 1.

All rings of the disk convoluted in a double spiral, of nearly equal breadth. Pores irregular, roundish, two to three on the breadth of each ring. Marginal spines numerous, twenty to thirty, of very different size, the largest conical, strong, about as long as the diameter of the disk, and on the base as broad as one ring.

Dimensions.—Diameter of the disk (with five rings) 0.12; breadth of each ring 0.01; pores 0.002 to 0.006.

Habitat.—Fossil in the rocks of Barbados.

15. Stylodictya clavata, Ehrenberg.

Stylodictya clavata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxiii. fig. 2.

All rings of the disk convoluted in a half spiral, of nearly equal breadth; each ring by four zigzag beams (crossed in two perpendicular diameters) divided into four equal quarters; the spiral line of each quarter ring halving both neighbouring quarters. Pores regular, circular, two on the breadth of each ring. Eight marginal spines short, conical, with thin pedicle; four perradial (as prolongations of the four internal beams) alternating with four interradial spines arising from the margin of the disk.

Dimensions.—Diameter of the disk (with five rings) 0.13; breadth of each ring 0.014; pores 0.003.

Habitat.—Fossil in the rocks of Barbados.

Genus 222. Stylochlamydium,^[261] Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with numerous (five or more, commonly eight to twelve) solid radial spines, regularly or irregularly disposed on the margin of the circular or polygonal disk; margin of the disk surrounded by a thin, porous (but not chambered), equatorial girdle.

The genus Stylochlamydium is intermediate between Perichlamydium (with which it was formerly united) and Stylodictya. It deals with the former in the peculiar equatorial girdle, with the latter in the radial spines of the disk margin, which pierce the girdle. To both these genera it shows slow transitions, and can hardly be subjected to a sharp definition.

Subgenus 1. Stylochlamys, Haeckel.

Definition.—All rings of the disk concentric, circular (or somewhat polygonal).

1. Stylochlamydium asteriscus, n. sp. (Pl. 41, fig. 10).

Perichlamydium asteriscus, Haeckel, 1879, MS.

All rings of the disk concentric, circular, or polygonal, with increasing breadth from the centre; the fifth ring twice as broad as the second. Pores irregular, roundish, three to four on the breadth of each ring; in the rings two to six times as large as in the equatorial girdle, which is half as broad or two-thirds as broad as the radius of the disk. Twelve bristle-shaped radial spines are connected by the girdle near to the points; four crossed spines arising from the central chamber; two others between these in each quadrant arising from the first ring.

Dimensions.—Diameter of the disk (with five rings) 0.15, with the girdle 0.25; breadth of the second ring 0.01, of the fifth ring 0.02; pores 0.001 to 0.005.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

2. Stylochlamydium limbatum, Haeckel.

Perichlamydium limbatum, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 43; Mikrogeol., 1854, Taf. xxii. fig. 20.

Perichlamydium limbatum, Haeckel, 1862, Monogr. d. Radiol., p. 494.

All rings of the disk concentric, circular, of equal breadth. Pores regular, circular, two on the breadth of each ring; twice to three times as large as the fine pores of the equatorial girdle, which is about half as broad as the radius of the disk. Twelve (or eleven) bristle-shaped radial spines are connected by the girdle near to the points, irregularly disposed.

Dimensions.—Diameter of the disk (with five rings) 0.12, with the girdle 0.2, breadth of each ring 0.01; pores 0.001 to 0.003.

Habitat.—Fossil in the Tertiary rocks of Sicily, Caltanisetta, Grotte.

3. Stylochlamydium venustum, Haeckel.

Perichlamydium venustum, Bailey, 1856, Amer. Journ., vol. xxii. p. 5, pl. i. figs. 16, 17.

Perichlamydium venustum, Haeckel, 1862, Monogr. d. Radiol., p. 495.

All rings of the disk concentric, circular, of equal breadth. Pores regular, circular, everywhere of nearly equal size, three on the breadth of each ring, a little smaller in the equatorial girdle, which is about as broad as the radius of the disk. Twenty to twenty-four bristle-shaped radial spines, irregularly disposed, proceed with their free points over the margin.

Dimensions.—Diameter of the disk (with four rings) 0.1, with the girdle 0.3; breadth of each ring 0.011; pores 0.002.

Habitat.—North Pacific, Kamtschatka, Bailey.

4. Stylochlamydium æquale, Haeckel.

Perichlamydium æquale, Stöhr, 1880, Palæontogr., vol. xxvi. p. 109, pl. v. fig. 2.

All rings of the disk concentric, circular, with increasing breadth from the centre; the sixth ring twice as broad as the second. Pores regular, circular, everywhere of equal size; on the breadth of the inner rings one, of the outer two, of the girdle three pores. Girdle only one-fourth as broad as the radius of the disk. About twenty bristle-shaped radial spines, irregularly disposed, are connected by the girdle near to the points.

Dimensions.—Diameter of the disk (with six rings) 0.11, with the girdle 0.17; breadth of the second ring 0.006, of the sixth 0.013; pores 0.006.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

Subgenus 2. Stylochlamyum, Haeckel.

Definition.—Rings of the disk all (or in part) not concentric, spirally convoluted or irregular.

5. Stylochlamydium perispirale, Haeckel.

Perichlamydium limbatum, var. Stöhr, 1880, Palæontogr., vol. xxvi. p. 109, Taf. v. fig. 1.

Inner rings of the disk concentric, circular, outer rings convoluted spirally, all rings of equal breadth. Pores regular, circular, two on the breadth of each ring, twice as large as in the equatorial girdle, which is about half as broad as the radius of the disk. Twelve to sixteen bristle-shaped radial spines, irregularly disposed, are connected by the girdle near to the points.

Dimensions.—Diameter of the disk (with six rings) 0.12, with the girdle 0.2; breadth of each ring 0.011; pores in the central disk 0.004, in the girdle 0.002.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

6. Stylochlamydium spongiosum, Haeckel.

Perichlamydium spongiosum, Stöhr, 1880, Palæontogr., vol. xxvi, p. 109, Taf. v. fig. 3.

Rings of the disk partly concentric, partly spiral, more or less irregular and often interrupted, with increasing breadth from the centre. Central part of the disk more or less spongy and obscure. Equatorial girdle half as broad as the radius of the chambered disk, with smaller pores than the latter, pierced by twenty to thirty thin, bristle-shaped radial beams, which proceed over the margin of the disk.

Dimensions.—Diameter of the disk (with ten rings) 0.2, with the girdle 0.3; breadth of the rings 0.005 to 0.015; pores 0.001 to 0.005.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms; also fossil in the Tertiary rocks of Barbados and Sicily.

Subfamily 5. Euchitonida, Haeckel.

Definition.—Porodiscida with two or more (commonly three or four) radial chambered or spongy arms on the margin of the concentrically annulated disk, situated in its equatorial plane (with or without a connecting patagium between the arms).

Genus 223. Amphibrachium,^[262] Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with two simple, undivided, chambered arms, opposite in one axis, without a patagium.

The genus Amphibrachium opens the long series of the Euchitonida, or of those Porodiscida which bear on the margin of the circular central disk a certain number of chambered arms, composed of a series of chambers which are separated by transverse septa. The first group or tribe of this subfamily is formed by the Amphibrachida, in which the disk bears only two arms opposite on the poles of one axis. The simplest form of these is Amphibrachium, in which both arms are simple, equal, and without a patagium or spongy connecticulum.

Subgenus 1. Amphibrachella, Haeckel.

Definition.—Both arms equal, of the same form and size, blunt at the distal end, without a terminal spine.

1. Amphibrachium sponguroides, n. sp.

Both opposite arms of the same form and size, nearly cylindrical, three times as long as broad, with six to eight transverse septa or joints, at the distal end rounded, blunt, without a terminal spine.

Dimensions.—Radius of each arm 0.22, breadth 0.065.

Habitat.—Antarctic Ocean, Station 154, surface.

2. Amphibrachium lanceolatum, n. sp.

Both arms equal, lanceolate, in the middle part three times as broad as at the two ends, two and a half times as long as broad, with eight to nine transverse septa, at the distal end blunt, without a terminal spine.

Dimensions.—Radius of each arm 0.3, greatest breadth 0.09.

Habitat.—Pacific, central area, Station 267, depth 2700 fathoms.

3. Amphibrachium dilatatum, n. sp. (Pl. 44, fig. 6).

Both arms equal, trapezoidal, somewhat broader than long, on the convex distal end three times as broad as on the narrow base, with five to six transverse septa, without a terminal spine. Central disk large, somewhat irregular, with three to four rings, twice as broad as the base of the arms.

Dimensions.—Radius of each arm 0.32, basal breadth 0.15, terminal breadth 0.44.

Habitat.—South Atlantic, off Patagonia, Station 319, surface.

Subgenus 2. Amphibrachidium, Haeckel.

Definition.—Both arms equal, of the same size and form, with terminal spines.

4. Amphibrachium amphilonche, n. sp.

Both arms equal, lanceolate, in the middle part four times as broad as at the two ends, twice as long as broad; on the distal end of each arm is a long conical spine.

Dimensions.—Radius of each arm (without terminal spine) 0.2, breadth 0.08.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

5. Amphibrachium capitatum, n. sp.

Both arms equal, club-shaped, three times as long as broad, in the outer distal half thickened, three times as broad as at the narrow base; on the distal end of each arm a strong, angular, terminal spine. (The form of the arms like that of Stephanastrum capitatum, Pl. 44, fig. 1.)

Dimensions.—Radius of each arm 0.22, basal breadth 0.02, terminal breadth 0.06.

Habitat.—Equatorial Atlantic, Station 347, surface.

6. Amphibrachium armatum, n. sp.

Both arms equal, four times as long as broad, in the thickened distal part twice as broad as at the base, thorny, with twenty to thirty larger spines on the distal end, and a very large pyramidal spine in the longitudinal axis. (The form of the arms like that of the odd arm in Euchitonia carcinus, Pl. 43, fig. 10.)

Dimensions.—Radius of each arm 0.24, basal breadth 0.03, distal breadth 0.06.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

Subgenus 3. Amphibrachoma, Haeckel.

Definition.—Both arms of different size or form, without terminal spines.

7. Amphibrachium indicum, n. sp.

Both arms club-shaped, but very different in size and form; larger arm three times as long and twice as broad as the smaller arm; the larger with nine joints slowly increasing in size, the smaller with four joints, rapidly increasing; the terminal joint three times as broad as the basal. Distal end blunt, rounded, without spines.

Dimensions.—Radius of the larger arm 0.24, of the smaller 0.08; distal breadth of the former 0.06, of the latter 0.03; basal breadth 0.015.

Habitat.—Indian Ocean, Ceylon, Haeckel, surface.

Subgenus 4. Amphibrachura, Haeckel.

Definition.—Both arms of different size or form, with terminal spines.

8. Amphibrachium clavula, n. sp.

Both arms different in size and form; larger arm club-shaped, four times as long as broad, at the distal end three times as broad as at the base, and twice as long as the smaller arm, which resembles a stalked knob, with thin basal peduncle and spherical distal part. Ends of the two arms thorny (with numerous smaller, and three to five larger spines); one very large conical terminal spine on each pole of the main axis.

Dimensions.—Radius of the larger arm 0.3, of the smaller 0.15; distal breadth of the former 0.06, of the latter 0.04; basal breath 0.02.

Habitat.—South Atlantic, Station 333, surface.

Genus 224. Amphymenium,^[263] Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with two simple, undivided, chambered arms, opposite in one axis, connected by a patagium.

The genus Amphymenium differs from the preceding Amphibrachium, its ancestral form, by development of a patagium or connecticulum between both arms. This forms a latticed or more spongy envelop, which surrounds either the middle part of the shell, or the whole shell with exception of the distal ends of both arms. If the envelop become very spongy, the shell may be confounded with the cylindrical Ellipside Spongocore (nearly allied to Spongurus); possibly also Ommatogramma of Ehrenberg belongs to this genus.

Subgenus 1. Ommatogramma, Ehrenberg (?).

Definition.—Both opposite arms of the same size and form, blunt, without terminal spines.

1. Amphymenium pupula, n. sp. (Pl. 44, fig. 8).

Both arms equal, twice as long as broad, three-jointed; the terminal joint egg-shaped, as large as both other joints together; distal end rounded, blunt. Patagium nearly complete, enveloping the arms with exception of the distal end. Perimeter nearly spindle-shaped.

Dimensions.—Radius of each arm 0.17, greatest breadth 0.06; transverse breadth of the patagium 0.13.

Habitat.—Pacific, central area, Station 273, depth 2350 fathoms.

2. Amphymenium naviculare, Haeckel.

? Ommatogramma navicularis, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 317; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. vi. fig. 7.

Both arms equal, three times as long as broad, spongy, not jointed; distal end a little club-shaped, blunt. Patagium nearly complete, enveloping the arms with exception of the distal end. Perimeter nearly lanceolate. The imperfect diagnosis and figure of Ehrenberg make it doubtful whether this species belongs to the Porodiscida (Amphymenium) or to the Spongodiscida (Spongobrachium) or perhaps to the Spongurida (Spongocore).

Dimensions.—Radius of each arm 0.1, greatest breadth 0.03; transverse breadth of the patagium 0.05.

Habitat.—North Pacific, Californian Sea, depth 2600 fathoms, Ehrenberg.

3. Amphymenium zygartus, n. sp. (Pl. 44, fig. 7).

Both arms equal, four times as long as broad, with seven to eight joints, slowly decreasing in size towards the blunt end. Patagium incomplete, protecting only the middle part of the shell on both sides; on each side two parallel lattice-plates, connected by transverse radial beams, perpendicular to the surface. Perimeter nearly rectilinear. (Resembles much certain forms of Zygartus, Pl. 40, but is a true Discoid, no Prunoid.) Compare also Pl. 45, fig. 8.

Dimensions.—Radius of each arm 0.2, greatest breadth 0.05; transverse breadth of the patagium 0.11.

Habitat.—Pacific, central area, Station 271, surface.

4. Amphymenium monstrosum, n. sp. (Pl. 44, fig. 11).

Both arms equal, little longer than broad, with six to seven convex joints. The axis of both arms is not common and straight, as in all other species of this genus, but broken, therefore the incomplete patagium, which envelops only two to three joints of the arms, is on one side convex, on the other side concave; it is formed by a simple lattice-plate, connected with the arms by numerous radial beams. This anomalous form, seen only once, may perhaps be a monstrosity of Euchitonia.

Dimensions.—Radius of each arm 0.12, greatest breadth 0.06; transverse breadth of the patagium 0.13.

Habitat.—South Pacific, Station 290, surface.

Subgenus 2. Ommathymenium, Haeckel.

Definition.—Both opposite arms of the same size and form, armed at the distal end with terminal spines.

5. Amphymenium amphistylium, n. sp. (Pl. 44, fig. 9).

Both arms equal, three times as long as broad, thickened towards the truncated distal end, and armed with a strong pyramidal terminal spine. Each arm with seven joints, separated by convex, transverse septa, and halved by a radial beam lying in the longitudinal axis. Patagium incomplete, cylindrical, enveloping only the middle part of the shell.

Dimensions.—Radius of each arm 0.18, greatest breadth 0.06; transverse breadth of the patagium 0.08.

Habitat.—North Atlantic, Station 354, surface.

6. Amphymenium fusiforme, n. sp.

Both arms equal, lanceolate, three times as long as broad in the width, with seven to eight joints. Distal end pointed, armed with a strong conical terminal spine. Patagium complete, enveloping the whole shell with exception of the terminal spines. Whole form spindle-shaped.

Dimensions.—Radius of each arm 0.2, greatest breadth 0.07; transverse breadth of the patagium 0.15.

Habitat.—South Atlantic, Station 330, surface.

Genus 225. Amphirrhopalum,^[264] Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with two chambered arms, opposite in one axis, without a patagium; one arm or both forked at the distal end.

The genus Amphirrhopalum differs from Amphibrachium, its ancestral form, by bifurcation of the distal ends of the arms, which may affect either both arms, or only one of them.

Subgenus 1. Amphirrhopalium, Haeckel.

Definition.—Both opposite arms of similar size and form, with blunt branches, without terminal spines.

1. Amphirrhopalum ximorphum, n. sp.

Both arms equal, in the proximal half simple, in the distal half forked, with six to seven transverse septa; distal end of each branch blunt, without terminal spine, somewhat broader than the base of the whole arm. Axis of the branches concavely curved. (Resembles Amphicraspedum maclaganium, Pl. 45, fig. 11, but wants the patagium.)

Dimensions.—Radius of the arms 0.18, basal breadth 0.065; terminal breadth of each branch 0.075.

Habitat.—North Pacific, off Japan, Station 240, surface.

2. Amphirrhopalum amphidicranum, n. sp.

Both arms equal, in the proximal half simple, in the distal half forked, with irregular septa; distal end of each arm blunt, without a terminal spine, smaller than the basal breadth of the arm. Axis of the branches straight. (Resembles Dicranastrum furcatum, Pl. 47, fig. 2, but without lateral arms.)

Dimensions.—Radius of each arm 0.15, basal breadth 0.03; terminal breadth of each branch 0.02.

Habitat.—Pacific, central area, Station 263, depth 2650 fathoms.

Subgenus 2. Amphirrhopella, Haeckel.

Definition.—Both opposite arms of similar size and form, with terminal spines.

3. Amphirrhopalum bigeminum, n. sp.

Both arms equal, in the proximal larger half simple, in the distal smaller half forked; each branch triangular, with a strong conical terminal spine. Axis of the branches straight. (Resembles Dicranastrum cornutum, Pl. 45, fig. 2, but without lateral arms.)

Dimensions.—Radius of the arms (without spines) 0.15, basal breadth 0.03; breadth of the bifurcation 0.08.

Habitat.—South Pacific, Station 284, surface.

4. Amphirrhopalum echinatum, n. sp. (Pl. 45, fig. 10).

Both arms equal, in the proximal smaller half simple, nearly square, in the distal larger half forked; the branches thorny, armed at the end with numerous spines, one larger on the terminal pole of the concavely curved arm-axis.

Dimensions.—Radius of the arms (without spines) 0.15, basal breadth 0.05; breadth of branches 0.03.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

Subgenus 3. Amphirrhopoma, Haeckel.

Definition.—Both opposite arms of different size or form, without terminal spines.

5. Amphirrhopalum ypsilon, n. sp.

Both arms very different. Larger arm simple, egg-shaped, twice as long as broad; smaller arm in the basal half simple, nearly square, in the distal half forked; both branches egg-shaped, blunt. (Resembles Amphicraspedum wyvilleanum, Pl. 45, fig. 12, but wants the patagium.)

Dimensions.—Radius of the larger simple arm 0.18, breadth 0.09; radius of the smaller forked arm 0.15, breadth of its branches 0.05.

Habitat.—Indian Ocean, Madagascar, Rabbe, surface.

Genus 226. Amphicraspedum,^[265] Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with two chambered arms, opposite in one axis, connected by a lateral patagium; one arm or both forked at the distal end.

The genus Amphicraspedum exhibits the same bifurcation of the arms as does Amphirrhopalum, but differs from this ancestral form in the development of a patagium, an external connecticulum between the arms, which envelops the disk totally or partially.

Subgenus 1. Amphicraspedon, Haeckel.

Definition.—Both arms of equal size and form, without terminal spines of the branches.

1. Amphicraspedum maclaganium, n. sp. (Pl. 45, fig. 11).

Both arms equal, in the proximal half simple, in the distal half forked, with six to seven transverse septa; distal end of each branch rounded, blunt, somewhat broader than the base of the whole arm. Divergent axes of both branches concavely curved. Patagium incomplete, with elliptical perimeter, enveloping only the middle part of the shell. I call this interesting species in honour of Miss Nellie Maclagan, the learned translator of several zoological papers from German into English.

Dimensions.—Radius of each arm 0.25, basal breadth 0.07; distal breadth of each branch 0.08; equatorial breadth of the patagium 0.25.

Habitat.—North Atlantic, off Halifax, Station 50, surface.

Subgenus 2. Amphicraspedina, Haeckel.

Definition.—Both arms of different size or form, without terminal spines on the branches.

2. Amphicraspedum wyvilleanum, n. sp. (Pl. 45, fig. 12).

Both arms different. Larger arm simple, egg-shaped, with eleven convex joints, one and a half times as long as broad; smaller arm in the basal half simple, triangular, with six cap-like joints, in the distal half forked; both branches egg-shaped, with five joints and blunt ends. Patagium nearly complete with four to five concave chamber-rows. Called in honour of Sir C. Wyville Thomson.

Dimensions.—Radius of the larger simple arm 0.18, breadth 0.08; radius of the smaller forked arm 0.16; breadth of the branches 0.05; transverse breadth of the patagium 0.2.

Habitat.—South Atlantic, Station 333, surface.

Subgenus 3. Amphicraspedula, Haeckel.

Definition.—Both arms of different size or form, with terminal spines of the branches.

3. Amphicraspedum murrayanum, n. sp. (Pl. 44, fig. 10).

Amphymenium murrayanum, Haeckel, 1879, MS. et Atlas (pl. xliv. fig. 10).

Both arms different in size; the larger one and a half times as long and broad as the smaller. Both arms triangular, forked at the broader distal end, with two very strong, conical, divergent, straight terminal spines. Patagium broad, incomplete, with circular perimeter. Called in honour of my friend Dr. John Murray.

Dimensions.—Radius of the larger arm (including the spines) 0.24, of the smaller 0.16; distance of the terminal points of the former 0.18, of the latter 0.09; diameter of the patagium 0.2.

Habitat.—North Atlantic, Færöe Channel, Gulf Stream, surface, John Murray.

Genus 227. Dictyastrum,^[266] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 830.

Definition.—Porodiscida with three simple, undivided, chambered arms, without a patagium; triangular shell regular, with three equal arms and three equal angles.

The genus Dictyastrum is the simplest form of the Trigonastrida, or of the Porodiscida, in which the margin of the central disk is furnished with three chambered arms. In Dictyastrum these are quite simple and regular, without a patagium, separated by equal angles, so that the whole shell represents a regular, equilateral triangle, if we connect the distal points of the arms by lines. The genus Dictyastrum, founded by Ehrenberg in 1860, differs from his Rhopalodictyum—after his own diagnosis—only by an insignificant difference in the form of the simple arms, which is scarcely a specific character. I therefore apply this name here in the above amended sense, seeing that the only figured species of Ehrenberg (Dictyastrum angulatum) occurs in two different, but externally very similar forms: one of these is a true Porodiscid (Dictyastrum) with two porous covering-plates and concentric rings; the other is a true Spongodiscid (Rhopalodictyum) with quite spongy, irregular network, and is probably identical with the Rhopalodictyum truncatum of Ehrenberg.

Subgenus 1. Dictyastrella, Haeckel.

Definition.—Arms with blunt ends, without terminal spines.

1. Dictyastrum angulatum, Ehrenberg.

Dictyastrum angulatum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 289, Taf. viii. fig. 18.

Arms nearly square with straight edges, towards the truncated end a little broader, about the same diameter as the triangular central disk. The figure of Ehrenberg seems to represent a Spongodiscid (Rhopalodictyum angulatum), but in the same locality (Philippine Sea) occurs also a true Dictyastrum of quite the same form, but with three to four concentric rings of the central disk, and with jointed arms.

Dimensions.—Radius of each arm (length from the centre to the distal end) 0.13; breadth of the truncated end 0.1.

Habitat.—Tropical Pacific, Philippine Sea, Station 200, depth 250 fathoms.

2. Dictyastrum bandaicum, Haeckel.

Rhopalastrum bandaicum, Harting, 1863, Mikr. Fauna Banda-Zee, p. 16, Taf. iii. fig. 45.

Arms nearly square, with convex edges, in the middle a little broader than at both ends, about half the diameter of the central disk. Differs from the nearly allied preceding species by the half size of the arms and the convex edges.

Dimensions.—Radius of each arm 0.12, its greatest breadth 0.07.

Habitat.—Tropical Pacific, Banda Sea, Harting.

3. Dictyastrum hexagonum, n. sp. (Pl. 43, fig. 7).

Rhopalastrum hexagonum, Haeckel, 1880, Atlas (pl. xliii. fig. 1).

Arms nearly triangular, one and a third times as broad at the distal end as long, and three times as broad as at the base. Central disk about the same diameter. In each arm six simple broad chambers. If we connect the six corners of the truncated distal ends by straight lines, we get a regular hexagon.

Dimensions.—Radius of each arm 0.17, basal breadth 0.06, terminal breadth 0.17.

Habitat.—Equatorial Atlantic, Station 347, surface.

4. Dictyastrum trirrhopalum, n. sp.

Arms club-shaped, five times as long as broad at the base, at the thickened end three times as broad as at the base. Diameter of the central disk equals half the length of the arms. (Similar to Rhopalastrum malleus, Pl. 43, fig. 1, but with three equal angles and much smaller disk.)

Dimensions.—Radius of each arm 0.25, basal breadth 0.04, distal breadth 0.12.

Habitat.—Pacific, central area, Station 273, surface.

Subgenus 2. Dictyastromma, Haeckel.

Definition.—Arms on the distal end provided with terminal spines.

5. Dictyastrum trispinosum, n. sp. (Pl. 43, fig. 5).

Rhopalastrum trispinosum, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. 5).

Arms trapezoid, at the rounded distal end twice as broad as at the base, with a strong and short, conical, terminal spine. Diameter of the circular central disk about equal to the length and the greatest breadth of the arms.

Dimensions.—Radius of each arm 0.15, basal breadth 0.06, distal breadth 0.11.

Habitat.—Equatorial Atlantic, Station 347, surface.

6. Dictyastrum triactis, Ehrenberg.

Dictyastrum triactis, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 306.

Arms rectilinear, four times as long as broad, with parallel edges, pointed at the distal end, with a short terminal spine. Diameter of the circular central disk equal to double the breadth of the arms.

Dimensions.—Radius of each arm 0.2, breadth 0.04.

Habitat.—Pacific, Philippine Sea, Station 206, depth 2100 fathoms.

7. Dictyastrum aculeatum, n. sp.

Arms lanceolate, three times as long as broad, twice as broad in the middle as at either end, with thorny surface and numerous conical terminal spines, one very large in the radius. Central disk triangular, about as broad as the arms. (Resembles Rhopalastrum arcticum, Pl. 43, fig. 6, but differs by the equal angles and the triangular disk.)

Dimensions.—Radius of each arm 0.2, breadth 0.06.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Genus 228. Rhopalastrum,^[267] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Porodiscida with three simple undivided, chambered arms, without a patagium; triangular shell bilateral, one odd arm opposite to the odd angle between two paired arms.

The genus Rhopalastrum, founded by Ehrenberg (1847) with a very insufficient diagnosis, is here retained for those Trigonastrida that agree in the generic characters with the only species figured by him, viz., Rhopalastrum lagenosum (compare my Monograph, 1862, p. 500). It comprises, therefore, such Euchitonida as agree with the preceding Dictyastrum in the simple form of the three arms and the absence of a patagium, but differ from it in the different size of the three angles, and often also in the divergent form and size of the three arms; one odd arm is opposite to the odd angle between the two paired arms.

Subgenus 1. Rhopalastrella, Haeckel.

Definition.—Arms with blunt ends, without terminal spines.

1. Rhopalastrum truncatum, Haeckel.

Rhopalastrum truncatum, Haeckel, 1862, Monogr. d. Radiol., p. 500, Taf. xxix. fig. 6.

Distance of both paired arms about half as large as their distance from the odd arm. All three arms nearly of the same form and size, very short and broad; their breadth nearly equals that of the roundish central disk, whilst their length reaches only one-fourth of it. End of the arms convex rounded, without spines.

Dimensions.—Radius of each arm 0.1, breadth 0.15.

Habitat.—Mediterranean (Messina), Atlantic (Canary Islands), surface, Haeckel.

2. Rhopalastrum pistillum, Stöhr.

Rhopalastrum pistillum, Stöhr, 1880, Palæontogr., vol. xxvi. p. 110, Taf. v. fig. 4.

Distance between the paired arms about two-thirds as large as their distance from the odd arm. All three arms nearly of the same form and size, about three times as long as the diameter of the central disk, at the base one-third as broad as at the convex rounded end, without spines. Stöhr has only observed a fragment with one arm; some perfect specimens, which I found in the Caltanisetta-rock, exhibited nearly the same form as Rhopalastrum malleus (Pl. 43, fig. 1), but differ from this by the smaller disk, the broader arms, and the smaller angle between the paired arms.

Dimensions.—Radius of all three arms 0.2; basal breadth of each arm 0.045, terminal breadth 0.13.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte (Stöhr), Caltanisetta (Haeckel).

3. Rhopalastrum malleus, n. sp. (Pl. 43, fig. 1).

Distance between the paired arms one and a third times as large as their distance from the odd arm. All three arms nearly of the same form and size, hammer-shaped, three times as broad at the truncated distal end as at the base. Central disk broader than the arms.

Dimensions.—Radius of each arm 0.25, basal breadth 0.05, distal breadth 0.15.

Habitat.—South Atlantic, Station 325, surface.

4. Rhopalastrum lagenosum, Ehrenberg.

Rhopalastrum lagenosum, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 43; Mikrogeol., 1854, Taf. xxii. fig. 22.

Rhopalastrum lagenosum, Haeckel, 1862, Monogr. d. Radiol., p. 501.

Flustrella bilobata, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 81.

Haliomma lagena, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 200.

Distance between the paired arms one and a half times as great as their distance from the odd arm. All three arms nearly of the same form and size, about one and a half times as long as the diameter of the central disk, at the base half as broad as at the convex rounded end, without spines. Ehrenberg has only observed a fragment with two paired arms; some perfect specimens with three arms, observed by me, differed from the nearly allied Rhopalastrum pistillum (from the same locality) by the larger disk, the broader arms, and the larger unpaired angle.

Dimensions.—Radius of all three arms 0.2, basal breadth 0.05, terminal breadth 0.09.

Habitat.—Fossil in Tertiary rocks of Sicily, Caltanisetta.

5. Rhopalastrum ypsilinum, n. sp. (Pl. 43, fig. 2).

Distance between the paired arms half as large as their distance from the odd arm. All three arms at the concavely curved distal end three times as broad as at the narrow base. Odd arm twice as long and broad as the paired arms. Central disk smaller than the latter. No terminal spines.

Dimensions.—Radius of the odd arm 0.32, of the paired arms 0.2; terminal breadth of the former 0.2, of the latter 0.12.

Habitat.—Indian Ocean, Cocos Islands, Rabbe, surface.

6. Rhopalastrum clavatum, n. sp.

Distance between the paired arms half as large as their distance from the odd arm. All three arms club-shaped, at the thickened, nearly spherical, distal end three times as broad as at the narrow base. Odd arm nearly twice as long and broad as the paired arms. Central disk equal to the distal knob of the latter. No terminal spines.

Dimensions.—Radius of the odd arm 0.3, of the paired arms 0.18; distal breadth of the former 0.16, of the latter 0.08.

Habitat.—South Atlantic, Station 332, surface.

7. Rhopalastrum irregulare, n. sp. (Pl. 43, fig. 8).

Distance between all three arm-points different. All three arms cylindrical, nearly of the same length, but of different form, irregularly curved, about four times as long as broad, with blunt ends.

Dimensions.—Length of each arm about 0.2, breadth 0.05.

Habitat.—Antarctic Sea, Station 157, depth 1950 fathoms.

Subgenus 2. Rhopalastromma, Haeckel.

Definition.—Arms on the distal end provided with one or more terminal spines.

8. Rhopalastrum martellum, n. sp.

Distance between all three arm-points nearly the same; but the odd arm is one and a half times as large as both paired arms, and is perpendicular to the common axis of the latter, therefore the shell has the form of a hammer. Each arm is twice as broad at the distal end as at the base, and armed with a conical terminal spine; the latter is vertical in the odd arm, horizontal in the paired arms.

Dimensions.—Radius of the odd arm 0.3, of the paired arms 0.15; distal breadth of the former 0.12, of the latter 0.06.

Habitat.—North Atlantic, Station 354, surface.

9. Rhopalastrum triceros, n. sp. (Pl. 43, fig. 4).

Distance between the paired arms about two-thirds as large as their distance from the odd arm. All three arms club-shaped, three times as broad at the thickened distal part as at the base, and armed with one single, conical, terminal spine. Odd arm of the same breadth, but twice as long as the paired arms.

Dimensions.—Radius of the odd arm 0.35, of the paired arms 0.2; basal breadth 0.04, distal breadth 0.12.

Habitat.—Pacific, central area, Station 274, surface.

10. Rhopalastrum hexaceros, n. sp. (Pl. 43, fig. 3).

Distance between the paired arms equals four-fifths of their distance from the odd arm. All three arms nearly of the same size, about square, a little broader at the truncated distal end, which is armed at both corners with a strong, conical, radial spine.

Dimensions.—Radius of each arm 0.2, basal breadth 0.1, distal breadth 0.12.

Habitat.—Indian Ocean, Ceylon, Belligemma, Haeckel, surface.

11. Rhopalastrum arcticum, n. sp. (Pl. 43, fig. 6).

Distance between the paired arms half as large as their distance from the odd arm, which is a little larger. All three arms of the same form, lanceolate, twice to three times as long as broad, twice as broad in the middle as at either end. Each arm with twelve to fourteen transverse septa, at the distal end with a bunch of conical spines, and one single, very large, pyramidal, terminal spine.

Dimensions.—Radius of each arm (without spine) 0.17, greatest breadth of it 0.05 to 0.06.

Habitat.—Arctic Ocean, lat. 83° 19' N., North Polar expedition of the "Alert."

Genus 229. Hymeniastrum,^[268] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Porodiscida with three simple, undivided, chambered arms, connected by a patagium; triangular shell regular, with three equal arms and three equal angles.

The genus Hymeniastrum was founded by Ehrenberg (1847) with a very incomplete diagnosis, and hitherto known only by one single species, figured by him as Hymeniastrum pythagoræ (Mikrogeol., 1854, Taf. xxxvi. fig. 31). This form occurs in two different states, externally quite identical; in one state the central disk (as figured, loc. cit.), is a simple lens or hollow disk, containing a medullary shell or "central chamber"; in the other state the central disk is composed of two concentric rings surrounding the "central chamber." We retain here the name Hymeniastrum for this latter state, expressed in the diagnosis given above, and call the former state (the Coccodiscid) Hymenactura (compare above, p. 473). One practical advantage, obtained in this way, is that all genera of Discoidea ending with "-astrum" belong to the Porodiscida. Hymeniastrum differs from Dictyastrum by the possession of a patagium, and from Euchitonia by the equal size of the angles and the arms.

Subgenus 1. Hymenastrella, Haeckel.

Definition.—Arms with blunt ends, without terminal spines.

1. Hymeniastrum leydigii, Haeckel.

Euchitonia leydigii, Haeckel, 1862, Monogr. d. Radiol., p. 510, Taf. xxxi. figs. 4, 5.

Hymeniastrum leydigii, Haeckel, 1881, Prodromus, p. 460.

Histiastrum trinacrium, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 843.

Arms twice as long as broad, two-thirds as broad at the base as at the blunt, nearly truncated distal end. Patagium nearly complete, perfectly filling out the interbrachial spaces, with six to seven regular, concave chamber-rows; only the truncate terminal faces of the arms free.

Dimensions.—Radius of the arms 0.15 to 0.18, breadth on their base 0.04 to 0.05, on their broadest distal end 0.06 to 0.07.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. Very common and variable.

2. Hymeniastrum köllikeri, Haeckel.

Euchitonia köllikeri, Haeckel, 1862, Monogr. d. Radiol., p. 511, Taf. xxxi. figs. 6, 7.

Hymeniastrum köllikeri, Haeckel, 1881, Prodromus, p. 460.

Arms nearly lanceolate, twice as long as broad, half as broad at the base as at the broadest middle part, pointed at the distal end. Patagium complete, enveloping the whole triangular disk, with irregular chamber-rows.

Dimensions.—Radius of the arms 0.2, breadth on their base 0.04, on the broadest part 0.08.

Habitat.—Mediterranean (Messina), surface.

3. Hymeniastrum gümbelii, Haeckel.

Stylactis gümbelii, Stöhr, 1880, Palæontogr., vol. xxvi. p. 112, Taf. vi. fig. 1.

Arms twice as long as broad, nearly twice as broad in the circular distal half as in the square proximal half. Patagium incomplete, circular, with eight to nine convex chamber-rows, enveloping only the proximal square halves of the arms; the lenticular distal halves remain free.

Dimensions.—Radius of the arms 0.14; breadth at the base 0.04, at the distal lenticular part 0.07.

Habitat.—Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.

4. Hymeniastrum euclidis, n. sp. (Pl. 43, fig. 13).

Euchitonia euclidis, Haeckel, 1881, Prodromus, p. 460 et Atlas (pl. xliii. fig. 13).

Arms one and a half times as long as broad, club-shaped, three times as broad in the oval distal part as in the narrow square proximal part. Patagium complete, enveloping the whole triangular disk, and also the convex ends of the arms, with eight to nine convex chamber-rows.

Dimensions.—Radius of the arms 0.18; breadth at the base 0.025, at the broadest distal part 0.07.

Habitat.—Pacific, central area, Stations 270 to 274, surface.

5. Hymeniastrum pythagoræ, Ehrenberg.

Hymeniastrum pythagoræ, Ehrenberg, 1854 (partim), Mikrogeol., Taf. xxxvi. fig. 31.

Arms nearly as broad as long, two-thirds as broad at the base as at the truncated distal end. Patagium incomplete, enveloping only the basal half of the arms, with four to five rectilinear parallel chamber-rows. (This form has the greatest resemblance to the figure given by Ehrenberg, loc. cit., but differs by the central disk, which is composed of two concentric rings surrounding the small central chamber; compare above Hymenactura pythagoræ, p. 474.)

Dimensions.—Radius of the arms 0.18; breadth at the base 0.08, at the truncated end 0.12.

Habitat.—Equatorial Atlantic, Station 347, depth 2250 fathoms.

6. Hymeniastrum archimedis, n. sp.

Arms nearly triangular, at the truncated, slightly convex end three times as broad as at the narrow base and one and a third times as broad as long; each arm with six simple chambers. Patagium incomplete, enveloping only the basal half of the arms with three to four convex chamber-rows. (Differs from Rhopalastrum hexagonum, Pl. 43, fig. 7, only by the patagium.)

Dimensions.—Radius of the arms 0.2; breadth at the base 0.07, at the truncated end 0.2.

Habitat.—Pacific, central area, Station 274, surface.

Subgenus 2. Hymenastromma, Haeckel.

Definition.—Arms at the distal end provided with radial spines.

7. Hymeniastrum ternarium, Haeckel.

Histiastrum ternarium, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 76, Taf. xxiv. fig. 2.

Arms two and a half times as long as broad, three times as broad at the truncated end as at the narrow base, with a strong, conical, radial spine at the end. Patagium incomplete, enveloping only the basal half of the arms, with three to four convex chamber-rows.

Dimensions.—Radius of the arms (without terminal spine) 0.02; breadth at the base 0.025, at the broadest terminal part 0.08.

Habitat.—Fossil in the rocks of Barbados.

8. Hymeniastrum trigonarium, n. sp.

Arms one and a half times as long as broad, a little broader at the rounded end than at the base, with three strong conical radial spines, one larger (in the radius of each arm) and two smaller on both sides of this. Patagium complete, with four to five rectilinear parallel chamber-rows, enveloping the whole arms (with exception of the terminal spines) and forming a perfect equilateral triangle.

Dimensions.—Radius of the arms (without terminal spines) 0.18; breadth at the base 0.1, at the distal part 0.12.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

Genus 230. Euchitonia,^[269] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 831 (sensu emendato).

Definition.—Porodiscida with three simple, undivided, chambered arms, connected by a patagium; triangular shell bilateral, one odd arm opposite to the odd angle between the two paired arms.

The genus Euchitonia, quite insufficiently characterised by Ehrenberg, was founded by him (1860) for one single species, afterwards (1872) described and figured as Euchitonia furcata. Retaining this species correctly as the type of this genus, I give to it here the above diagnosis. In my Monograph (1862, p. 503) I described seven Mediterranean species of Euchitonia. Three of these have in common the characters according to the present diagnosis: Euchitonia mülleri, Euchitonia virchowii, Euchitonia beckmanni; two others appertain (on account of the regular, not bilateral form) to Hymeniastrum, and two others (on account of the forked, not simple arms) to Trigonastrum. Afterwards (1880) three true fossil species of Euchitonia were described by Stöhr (Euchitonia cruciata, Euchitonia zittelii, and Euchitonia acuta). Some species of this genus are cosmopolitan, and appertain to the most common and everywhere represented Discoidea.

Subgenus 1. Stylactis, Ehrenberg, 1872 (loc. cit.).

Definition.—Arms with blunt ends, without terminal spines.

1. Euchitonia furcata, Ehrenberg.

Euchitonia furcata, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 308; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. vi. iii. fig. 6.

Distance between the paired arms about half as large as their distance from the odd arm. All three arms nearly of the same size and form, about twice as long as broad, one and a half times at the blunt convex end as broad as at the base. Patagium incomplete, with concave chamber-rows and irregular network, only enveloping the basal half of the arms.

Dimensions.—Radius of all three arms 0.15, basal breadth of each arm 0.04, terminal breadth 0.06.

Habitat.—North Pacific, Californian Sea, depth 2600 fathoms, Ehrenberg.

2. Euchitonia mülleri, Haeckel.

Euchitonia mülleri, Haeckel, 1862, Monogr. d. Radiol., p. 508, Taf. xxx. figs. 5-10.

Euchitonia mülleri, Stöhr, 1880, Palæontogr., vol. xxvi. p. 110, Taf. v. fig. 5.

Distance between the paired arms about two-thirds as large as their distance from the odd arm, which is somewhat larger. Length of the arms equals two and a half times the breadth of the blunt convex end or five times the breadth of the base. Patagium with concave chamber-rows, nearly complete, enveloping the arms with exception of the terminal face. (This common species is very variable; compare my Monograph.)

Dimensions.—Radius of all three arms 0.16 to 0.22, basal breadth 0.03 to 0.05, terminal breadth 0.06 to 0.08.

Habitat.—Cosmopolitan; one of the most common Discoidea in all seas, on the surface as well as at different depths; also fossil in the Tertiary rocks of Barbados and Sicily.

3. Euchitonia triangulum, Haeckel.

Stylactis triangulum, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 320; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. viii. fig. 9.

Stylactis triangulum, Stöhr, 1880, Palæontogr., vol. xxvi. p. 113, Taf. vi. fig. 2.

Distance between the paired arms about two-thirds as large as their distance from the odd arm. All three arms nearly of the same size and form, about one and a half times as long as broad, nearly as broad at the base as at the blunt rounded end. Patagium incomplete, with convex chamber-rows, enveloping about two-thirds of the arms.

Dimensions.—Radius of all three arms 0.15, basal breadth 0.05, terminal breadth 0.06.

Habitat.—Pacific and Atlantic, Stations 253, 272, 354, surface; also fossil in the Tertiary rocks of Barbados and Sicily.

4. Euchitonia cruciata, Stöhr.

Euchitonia cruciata, Stöhr, 1880, Palæontogr., vol. xxvi. p. 111, Taf. v. fig. 7.

Distance between the paired arms about one and a half times as large as their distance from the odd arm, which is a little larger. Length of the arm nearly equals twice the breadth, which is the same at the base and at the rounded blunt ends. Patagium incomplete, with concave chamber-rows, enveloping only the base of the arms, and forms between them three other smaller arms; therefore the whole shell forms six angles with six alternating arms.

Dimensions.—Radius of all three arms 0.15, basal breadth 0.05.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

5. Euchitonia lanceolata, n. sp. (Pl. 43, fig. 9).

Distance between the paired arms about one and a third times as large as their distance from the odd arm. All three arms nearly of the same size and form, three times as long as broad, lanceolate, much broader in the middle part than at both ends; distal end cuspidate, but not spiny. Patagium incomplete, with convex chamber-rows, envelops about two-thirds of the arms.

Dimensions.—Radius of all three arms 0.18, greatest breadth (in the width) 0.06.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

6. Euchitonia zittelii, Haeckel.

Stylactis zittelii, Stöhr, 1880, Palæontogr., vol. xxvi. p. 112, Taf. v. fig. 8.

Distance between the paired arms about one-fifth as large as their distance from the odd arm. All three arms nearly of the same size and form, in the proximal half thinner and nearly square, in the distal half thicker and circular; the latter half twice to three times as broad as the former. Patagium incomplete, with convex chamber-rows, envelops only the proximal square half of the arms.

Dimensions.—Radius of all three arms 0.15, basal breadth 0.03, terminal breadth 0.08.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

7. Euchitonia stöhrii, n. sp. (Pl. 43, fig. 12).

Distance between the paired arms about four-fifths as large as their distance from the odd arm, which is one and a half times as long as the former. Arms about three times as long as broad, twice as broad in the distal half as in the proximal half, with rounded blunt ends. Patagium complete, with concave chamber-rows, enveloping the whole shell, also the ends of the arms.

Dimensions.—Radius of the paired arms 0.2, of the odd arm 0.25; basal breadth 0.03, distal breadth 0.06.

Habitat.—Fossil in the rocks of Barbados and of Nicobar Islands, Haeckel. Indian Ocean, Cocos Islands (Rabbe). Also in the Central Pacific, Station 267.

8. Euchitonia beckmannii, Haeckel.

Euchitonia beckmannii, Haeckel, 1862, Monogr. d. Radiol., p. 505, Taf. xxxi. fig. 1.

Distance between the paired arms scarcely half as large as their distance from the odd arm, which is somewhat larger. Each arm with six simple broad chambers (without radial septa), the terminal chambers semilunar, convex, blunt, four times as broad as the first (basal) chamber. Patagium incomplete, with convex chamber-rows, enveloping the arms with exception of the broad blunt terminal face.

Dimensions.—Radius of the paired arms 0.15, of the odd arm 0.18; basal breadth 0.02 to 0.03, terminal breadth 0.1 to 0.15.

Habitat.—Mediterranean (Messina), Haeckel, surface.

9. Euchitonia virchowii, Haeckel.

Euchitonia virchowii, Haeckel, 1862, Monogr. d. Radiol., p. 503, Taf. xxx. figs. 1-4.

Histiastrum fasciatum, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 842.

Distance between the paired arms about half as large as their distance from the odd arm, which is somewhat larger. Each arm with six broad chambers, bisected by a radial septum; the terminal chamber convex, blunt, twice as broad as the basal chamber. Patagium incomplete, with concave chamber-rows, enveloping the arms with exception of the broad blunt terminal face.

Dimensions.—Radius of the paired arms 0.15, of the odd arm 0.16; basal breadth 0.05, terminal breadth 0.1 to 0.12.

Habitat.—Mediterranean (Messina), Atlantic (Canary Islands).

Subgenus 2. Pteractis, Ehrenberg, 1872 (loc. cit.).

Definition.—Arms provided with radial spines at the distal end.

10. Euchitonia elegans, Haeckel.

Pteractis elegans, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 299, Taf. viii. fig. 3.

Distance between the paired arms half as large as their distance from the odd arm. This latter is straight, while both the former are concavely curved towards the middle line. Arms five times as long as broad, at the distal end pointed and armed with a short conical terminal spine. Patagium nearly complete, enveloping four-fifths of the arms, with four to five concave chamber-rows.

Dimensions.—Radius of the arms 0.2, breadth of them 0.03.

Habitat.—Tropical Pacific, Philippine Sea, depth 3300 fathoms (Ehrenberg).

11. Euchitonia carcinus, n. sp. (Pl. 43, fig. 10).

Distance between the paired arms scarcely one-fourth as great as their distance from the odd arm. This latter is straight, twice as long as the former, which are concavely curved towards the middle line. The odd arm is three times as broad at the distal end as at the narrow base. The end of each arm is furnished with a strong triangular radial spine and a group of smaller spines. Patagium incomplete, with two to three concave chamber-rows, enveloping only the basal half of the arms.

Dimensions.—Radius of the paired arms 0.15, breadth 0.03; radius of the odd arm 0.3, breadth on its base 0.02, on its distal end 0.07.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

12. Euchitonia acuta, Stöhr.

Euchitonia acuta, Stöhr, 1880, Palæontogr., vol. xxvi. p. 111, Taf. v. fig. 6.

Distance between the paired arms two-thirds as great as their distance from the odd arm. All three arms nearly of the same size and form, two and a half times as long as broad, nearly lanceolate, at their broadest part one and a half times as broad as at their base. Patagium complete, enveloping the whole triangular disk, with five to six concave chamber-rows. In the figure of Stöhr the ends of the arms are simply pointed, while I find in the same fossil form a short terminal conical spine.

Dimensions.—Radius of all three arms 0.14; breadth at the base 0.04, at the broadest part 0.06.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte (Stöhr), Caltanisetta (Haeckel).

13. Euchitonia ypsiloides, Haeckel.

Histiastrum ypsiloides, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 843.

Distance between the paired arms two-thirds as great as their distance from the odd arm, which is somewhat larger. Length of the arms equals five times the breadth of the narrow base, which is half that of the distal end; this latter is armed with three to five short conical spines. Patagium complete, with six to seven concave chamber-rows, enveloping the whole arms with the exception of the terminal spines. (Differs from Euchitonia mülleri almost solely by the possession of terminal spines.)

Dimensions.—Radius of the arms 0.18 to 0.2; breadth at the base 0.04, at the distal end 0.08.

Habitat.—Mediterranean (Messina), Atlantic (Canary Islands), surface.

14. Euchitonia echinata, n. sp. (Pl. 43, fig. 11).

Distance between paired arms three-fourths as great as their distance from the odd arm, which is somewhat larger. Arms one and a half times as long as broad, somewhat constricted in the middle part, armed at the rounded ends with numerous (thirty to forty) strong, conical spines. Patagium complete, with four or five rectilinear parallel chamber-rows, enveloping the whole of the arms with the exception of the spiny ends.

Dimensions.—Radius of the arms (without spines) 0.2, breadth 0.06 to 0.09.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

Genus 231. Chitonastrum,^[270] Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with three forked, chambered arms, without a patagium. (Arms and angles between them either equal or unequal.)

The genus Chitonastrum differs from its ancestral form, Dictyastrum, by the bifurcation of the distal ends of the arms. The few species of this genus are partly regular (like Dictyastrum), partly bilateral (like Rhopalastrum). If the number of species increases much, these two subgenera may be separated into two genera: Chitonastrella corresponding to the former, Chitonastromma to the latter.

Subgenus 1. Chitonastrella, Haeckel.

Definition.—All three arms of the same size and form, equidistant; fundamental form of the shell therefore an equilateral triangle.

1. Chitonastrum triglochin, n. sp.

All three arms equal and equidistant. Each arm has the form of an isosceles triangle, twice as high as broad; the truncated apex of the triangle is inserted into the large central disk, whilst its distal base (four times as broad) is divided by a deep incision (half as long as the arm). Each arm with ten to twelve joints, simple in its basal half, double in its distal half. Axes of the six branches straight. (Resembles Trigonastrum regulare, Pl. 43, fig. 16, but differs in the absence of a patagium.)

Dimensions.—Radius of each arm 0.24, greatest breadth 0.11, basal breadth 0.03.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

2. Chitonastrum bathybium, n. sp.

All three arms equal and equidistant, in the basal two-thirds simple, rectilinear, three times as long as broad, in the distal third forked, both branches equal, straight, blunt, half as broad as the basal part.

Dimensions.—Radius of each arm 0.18, basal breadth 0.04, breadth of the branches 0.02.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Subgenus 2. Chitonastromma, Haeckel.

Definition.—One odd arm different in size or form from the two other arms, which are paired; distance between them different; fundamental form of the shell therefore a bilateral, isosceles triangle.

3. Chitonastrum jugatum, n. sp. (Pl. 43, fig. 14).

Dictyastrum jugatum, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. 14).

Arms very different; odd arm club-shaped, twice as long as broad, at the blunt distal end twice as broad as at the base; its axis is perpendicular to the common axis of both paired arms, which are only two-thirds as long, not so broad, and in the distal half divided into two branches; the anterior branch is straight, nearly horizontal, the posterior shorter and curved backwards.

Dimensions.—Radius of the odd arm 0.2, of the paired arms 0.15; distal breadth of the former 0.08, basal breadth 0.04; breadth of the paired arms 0.04.

Habitat.—South Atlantic, Station 325, surface.

4. Chitonastrum dicranoides, n. sp.

All three arms in the basal half simple, nearly square, in the distal half forked; branches straight, blunt. Odd arm twice as large as the paired arms; angle between the latter larger than the angles between them and the odd arm. (The form of the arms resembles Dicranastrum furcatum, Pl. 47, fig. 2.)

Dimensions.—Radius of the odd arm 0.24, of the paired arms 0.12; basal breadth 0.06.

Habitat.—North Atlantic, Station 353, surface.

5. Chitonastrum lyra, n. sp. (Pl. 43, fig. 15).

Dictyastrum lyra, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. 15).

All three arms forked and nearly of the same size, but different in form and position. The distance between the branches of the two paired arms is only one-fourth of the distance between them and the odd arm. Each arm in the basal two-thirds is simple, with eleven to twelve transverse septa, in the distal third forked, each branch with four to five transverse septa. The branches of each arm are curved convexly one to another, ending obtusely. The axis of the simple proximal part is straight in the odd arm, in the paired arms curved concavely towards the middle line. In the figured specimen, which I observed living in Portofino (in September 1880), the central chamber of the central disk and the first surrounding ring were filled with the nucleus of the cell; both external rings were filled (like all chambers of the arms) with pink oil-globules of the red central capsule. From the mantle, enveloping the shell, radiated innumerable fine pseudopodia (much too short in the figure), and between the two paired arms a long "sarcode-flagellum."

Dimensions.—Radius of each arm 0.16; greatest breadth of the odd arm 0.04; basal breadth of the paired arms 0.02; distance of both branches of each arm 0.08.

Habitat.—Mediterranean, Portofino, near Genoa, Haeckel.

Genus 232. Trigonastrum,^[271] n. gen.

Definition.—Porodiscida with three forked, chambered arms, connected by a patagium. (Arms and angles between them either equal or unequal.)

The genus Trigonastrum differs from the preceding Chitonastrum, its ancestral form, in the development of a patagium between the arms. It bears therefore to the latter the same relation that Euchitonia does to Rhopalastrum.

Subgenus 1. Trigonastrella, Haeckel.

Definition.—All three arms of the same size and form, equidistant; fundamental form of the shell therefore a regular, equilateral triangle.

1. Trigonastrum regulare, n. sp. (Pl. 43, fig. 16).

Chitonastrum regulare, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. 16).

All three arms equal and equidistant. Each arm has the form of an isosceles triangle, twice as high as broad, the truncated apex of which is inserted into the large circular central disk, whilst its distal base (four times as broad) is divided by a deep incision (half as long as the arm). Each arm with ten to twelve joints. Patagium between the arms nearly complete, spongy. (Differs from Chitonastrum triglochin mainly in the possession of a patagium.)

Dimensions.—Radius of each arm 0.24, greatest breadth 0.11, basal breadth 0.03; length of the sides of the regular triangle 0.45.

Habitat.—Pacific, central area, Station 274, surface.

Subgenus 2. Trigonastromma, Haeckel.

Definition.—One odd arm different in form or size from the other two arms, which are paired; distance between them different; fundamental form of the shell therefore an isosceles triangle.

2. Trigonastrum krohnii, Haeckel.

Euchitonia krohnii, Haeckel, 1862, Monogr. d. Radiol., p. 507.

All three arms different; distance between the two paired arms smaller than their distance from the odd arm. Odd arm with six joints. Each paired arm with seven joints, increasing in breadth towards the distal end. Odd arm and one paired arm forked at the end, the other paired arm simple. Patagium nearly complete. (The asymmetry in this form may perhaps be an individual anomaly, as also in Myelastrum anomalum, Pl. 47, fig. 9.)

Dimensions.—Radius of the arms about 0.13 to 0.16, breadth 0.05 to 0.08.

Habitat.—North Atlantic, Funchal, Madeira, Krohn, surface.

3. Trigonastrum gegenbauri, Haeckel.

Euchitonia gegenbauri, Haeckel, 1862, Monogr. d. Radiol., p. 506, Taf. xxxi. figs. 2, 3.

Arms different; distance between the paired arms larger than their distance from the odd arm, which is one-third shorter. Odd arm egg-shaped, simple, with seven joints, undivided. Both paired arms equal, with ten joints, in the distal third forked. Patagium nearly complete.

Dimensions.—Radius of the odd arm 0.14, greatest breadth 0.08; radius of the paired arms 0.2.

Habitat.—Mediterranean (Messina), Haeckel, surface.

Genus 233. Stauralastrum,^[272] n. gen.

Definition.—Porodiscida with four simple, undivided, chambered arms, without a patagium; quadrangular shell a regular cross, with four equal arms placed at right angles.

The genus Stauralastrum is the most simple form of the Tessarastrida, or of those Porodiscida in which the margin of the central disk is armed with four chambered arms. In Stauralastrum these four arms are quite simple and equal, without a patagium, separated by four right angles, so that the whole shell represents a regular rectangular cross. If we connect the distal points of the arms by lines, we get a complete square. (In my Prodromus, 1881, the species of this genus were united with Hagiastrum, which genus I now retain for the simple bilateral Tessarastrida.)

Subgenus 1. Stauralastrella, Haeckel.

Definition.—Ends of the arms blunt, without terminal spines.

1. Stauralastrum cruciforme, n. sp. (Pl. 45, fig. 6).

Arms very thin, nearly linear, four to five times as long as broad, of equal breadth at the base and at the truncated distal end; their breadth equals one-third of the radius of the central disk. Edges of the arms parallel.

Dimensions.—Radius of each arm 0.8, breadth 0.016.

Habitat.—South Pacific, Station 293, surface.

2. Stauralastrum lanceolatum, n. sp.

Arms lanceolate, three times as long as broad, in their middle part three times as broad as at both ends; their greatest breadth nearly equals the diameter of the central disk. (The arms have the same form as in Euchitonia lanceolata, Pl. 43, fig. 9.) Edges of the arms convex.

Dimensions.—Radius of each arm 0.3, greatest breadth (in the middle part) 0.08.

Habitat.—Pacific, central area, Station 273, depth 2350 fathoms.

3. Stauralastrum ordo, n. sp.

Arms trapezoid, about as long as broad, twice as broad at their truncated distal end as at the base; their basal breadth equals the radius of the central disk, which exhibits two to three rings. (The arms have nearly the same form as those in Hagiastrum mosis, Pl. 45, fig. 3.) Edges of the arms rectilinear, divergent towards the ends.

Dimensions.—Radius of each arm 0.12, basal breadth 0.04, distal breadth 0.08.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

4. Stauralastrum clavigerum, n. sp.

Arms twice as long as broad, in their distal half lenticular, nearly circular, twice as broad as in their square proximal half; their distal breadth equals the diameter of the central disk, which exhibits three to four rings. Edges of the arms concave.

Dimensions.—Radius of each arm 0.2, basal breadth 0.04, distal breadth 0.08.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

5. Stauralastrum dilatatum, n. sp.

Arms of nearly equal length and breadth, at their convex distal end three times as broad as at their narrow base; their distal breadth three times as large as the radius of the central disk, which exhibits three to four rings. (Resembles Histiastrum quadrigatum, Pl. 46, fig. 3, but has no patagium.) Edges of the arms concave.

Dimensions.—Radius of each arm 0.15, basal breadth 0.04, terminal breadth 0.12.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

Subgenus 2. Stauralastromma, Haeckel.

Definition.—Ends of the arms with one or more terminal spines.

6. Stauralastrum rhopalophorum, n. sp. (Pl. 45, fig. 1).

Hagiastrum rhopalophorum, Haeckel, 1881, Prodromus, p. 460.

Arms cylindrical, eight times as long as broad at their base, at their distal end club-shaped, three times as broad as at their base; their distal breadth twice as large as the diameter of the central disk, which exhibits two to three rings. Surface thorny, with larger spines towards the end, and one radial, very strong, angular terminal spine. Edges of the arms parallel.

Dimensions.—Radius of each arm (without terminal spine) 0.32, basal breadth 0.03, terminal breadth 0.1.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

7. Stauralastrum antiquum, n. sp.

Rhopalastrum sp. Bury, 1862, Polycystins of Barbados, pl. xiv. fig. 5.

Arms six times as long as broad at their base, in their distal half nearly spherical, three times as broad as in their cylindrical basal half; their distal breadth nearly equals the diameter of the central disk which exhibits three to four rings. On the end of each arm one strong, angular, terminal spine. (Differs from the preceding species by larger central disk and stouter arms, also by less developed spines.) Edges of the arms parallel.

Dimensions.—Radius of each arm 0.25, basal breadth 0.04, terminal breadth 0.12.

Habitat.—Fossil in the Barbados rocks; and living in the depths of the Central Pacific, Station 266, depth 2750 fathoms.

8. Stauralastrum staurolonche, n. sp.

Arms four times as long as broad at their base, gradually increasing towards their truncated end, which is one and a half times as broad as their base; their distal breadth equals the radius of the central disk, which exhibits four to five rings. At the end of each arm is a very strong conical terminal spine. (Resembles Histiastrum quaternarium, Abhandl. k. Akad. Wiss. Berlin, 1875, Taf. xxiv. fig. 3, but has no patagium.) Edges of the arms rectilinear, divergent.

Dimensions.—Radius of each arm 0.25, basal breadth 0.045, distal breadth 0.07.

Habitat.—Fossil in the Barbados rocks; and living in the depth of the Equatorial Atlantic, Station 348, depth (2450) fathoms.

9. Stauralastrum horridum, n. sp.

Arms three times as long as broad at their base, gradually increasing towards their rounded end, which is twice as broad as their base, their distal breadth equals the diameter of the central disk, which exhibits four to five rings. Surface thorny, at the distal end of each arm is a group of twenty to twenty-five smaller and five to six larger, straight, conical spines. Edges of the arms rectilinear, divergent.

Dimensions.—Radius of each arm 0.15, basal breadth 0.05, distal breadth 0.1.

Habitat.—Pacific, central area, Station 270, depth 2925 fathoms.

Genus 234. Hagiastrum,^[273] Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with four simple, undivided, chambered arms, without a patagium; quadrangular shell bilateral, two opposite arms of the main axis (or principal arms) different from the two others (or lateral arms).

The genus Hagiastrum, as here defined, was formerly united by me with the foregoing Stauralastrum, but differs from it by the bilateral or symmetrical form. Whilst in the latter all four arms and the four angles between them are equal, they are here differentiated into pairs.

Subgenus 1. Hagiastrella, Haeckel.

Definition.—Both longitudinal arms of equal size and form.

1. Hagiastrum buddhae, n. sp. (Pl. 45, fig. 5).

Cross rectangular. Both longitudinal arms of equal size, twice as long as the transverse arms; all arms smooth, club-shaped, twice as broad at their globose distal part as at their base, each with three large conical terminal spines.

Dimensions.—Radius of the principal arms 0.4, of the lateral arms 0.2; basal breadth 0.06, distal breadth 0.12.

Habitat.—Indian Ocean, Belligemma, Ceylon, surface, Haeckel.

2. Hagiastrum bramae, n. sp.

Cross rectangular. Both longitudinal arms of equal size, one and a half times as long as the transverse arms; all arms thorny, club-shaped, at their pear-shaped distal part three times as broad as at their base, provided with numerous conical spines, one larger terminal spine at their distal point. (Resembles Stauralastrum rhopalophorum, Pl. 45, fig. 1, but is distinguished by the different size of the arm-pairs, and by the stronger spines.)

Dimensions.—Radius of the principal arms 0.3, of the lateral arms 0.2; basal breadth 0.04, distal breadth 0.12.

Habitat.—Indian Ocean, off Maldive Islands, surface, Haeckel.

Subgenus 2. Hagiastromma, Haeckel.

Definition.—The two longitudinal arms different in size or form.

3. Hagiastrum mosis, n. sp. (Pl. 45, fig. 3).

Cross rectangular. All four arms nearly isosceles, triangular, at their narrow base half as broad as at their truncated, concavely fluted, distal end. The posterior principal arm with twelve to thirteen joints, twice as long as the anterior arm, which has six to seven joints and is one and a half times as long as the two lateral arms (with four to five joints).

Dimensions.—Radius of the posterior arm 0.3, of the anterior 0.15, of the lateral arms 0.1; basal breadth 0.05, terminal breadth 0.1.

Habitat.—Mediterranean (Smyrna), surface, Haeckel.

4. Hagiastrum mohammedis, n. sp.

Cross with unequal angles, the anterior little smaller than the posterior. All four arms club-shaped, thorny, three times as broad at their globose distal end as at their narrow base, and furnished with ten to twelve conical spines. Posterior principal arm twice as long as the anterior, and four times as long as the rudimentary lateral arms.

Dimensions.—Radius of the posterior arm 0.4, of the anterior 0.2, of the lateral arms 0.1; basal breadth 0.02 to 0.03, distal breadth 0.06 to 0.1.

Habitat.—Philippine Sea, Samboangan, Station 200, surface.

5. Hagiastrum christi, n. sp.

Cross with unequal angles, the anterior somewhat smaller than the posterior. All four arms of similar form, lanceolate, in their middle twice as broad as at either obtuse end. The posterior principal arm with twelve joints, one and a half times as long as the anterior (with nine joints) and twice as long as the two lateral arms (each with six joints). The form and structure of the arms in this species are nearly the same as in Tessarastrum straussi (Pl. 45, fig. 8); but the arms are broader in the middle, and are not connected by a patagium.